1. Field of the Invention
The present invention relates to a seal assembly for sealing at least one negative or positive pressure zone which adjoins a perforated surface which moves in a movement direction in a paper, tissue or cardboard machine.
2. Description of the Related Art
In practical applications seal assemblies of this type are used in the forming section as well as in the press section and/or the drying section of a respective paper machine, where they can be utilized in suction rolls or blow rolls.
Suction rolls of this type can, for example, be used as a pick-up suction roll or as a suction guide roll. There are applications wherein the paper, tissue or cardboard web—referred to in this document simply as a web—runs with or without support of fabrics or felts. The suction rolls comprise, as a rule, stationary inside suction boxes, which form for example adjustable zones with at least one pressure level. Sealing of the pressure- or vacuum zones in the direction of fabric travel and in the axial direction occurs through sealing elements which, if positionable, can be mounted in adjustable receptacles, for example so-called “format slides”. The moving surface in this case is consistent with the inside surface of the roll shell and as a rule is curved circularly.
The sealing elements which, due to their elongated shape, are also referred to as sealing strips contact the roll shell at the edge of a positive or negative pressure zone in the axial direction as well as also in the circumferential direction and thereby seal the zone. The web is held in the circumferential region of the negative pressure zone on the roll circumference through suction bores in the roll shell. The suction chamber often serves to also extract moisture from the web.
A suction roll is known from DE 10 2009 000 371 A1 whose suction box format is changeable through sealing element receptacles which laterally limit the suction zone and which are adjustable axially as well as in circumferential direction.
In order to achieve high running time efficiency it is important, among other things, to ensure a stable web run. Nevertheless, in many, in particular in graphic paper machines, web run problems occur. Therefore, after separation from the felt, in other words lifting of the felt on one web side or lifting of the web edge off of the felt, an unstable paper edge or even a raised edge, manifests itself.
Tests have shown that the adjustment of the suction on the web with the suction rolls, in particular with the suction felt guide roll has a significant influence on the edge characteristics of the paper. In order to ensure an optimum vacuum build-up on the paper, the “format slides” on the suction felt guide rolls and the pick-up rolls must be adjusted precisely, in particular transverse to the direction of web travel, in other words axially.
In machines currently in use however, the exact position of the format slide relative to the paper edge is not known since the adjustment of the web width occurs earlier in the production sequence, at the former (edge seam) and is not in direct relation to the adjustment of the format slide. In order to establish the position, the web edge must be determined relative to a fixed point of the roll (for example the roll edge). Then, the relative distance of the format slide to the paper edge must be determined by means of the geometric design data of the roll. This process is time consuming and at the same time awkward. If during the life span of a felt, adjustments are made to the edge seam, then the web width changes and the relative format slide positions become increasingly obscure if the adjustment is not reacted to immediately.
What is needed in the art is to simplify the adjustability of the receptacle for positioning the sealing element.